# CONFIG_X86_INTEL_PSTATE is not set
====================================

  http://cateee.net/lkddb/web-lkddb/X86_INTEL_PSTATE.html

  May 2013: intel devs say stop using on demand
  https://plus.google.com/+TheodoreTso/posts/2vEekAsG2QT

  norgo reports issues with modern intel processors
  https://bugzilla.kernel.org/show_bug.cgi?id=93521

  So at least disabling INTEL_PSTATE for older kernels makes sense (4.1-).


shared memfd open() failed: Function not implemented
====================================================

  This error means you should use kernel 3.17+

    memfd is a kernel feature (introduced in version 3.17) to allocate temporary files
    that do not depend on /tmp or /dev/shm. More info:
    https://dvdhrm.wordpress.com/2014/06/10/memfd_create2/

forcepae kernel param
=====================

  It first appeared in k3.15:
     http://lxr.free-electrons.com/source/Documentation/kernel-parameters.txt?v=3.15
 
  It looks like there's no need to produce non-pae kernels anymore because
  even ancient cpus support PAE... even some cpus that don't report
  the PAE flag (Pentium M, Celeron M cpus):
  
  > Many Pentium M systems disable PAE but may have a functionally usable PAE
  > implementation. This adds the "forcepae" parameter which bypasses the boot
  > check for PAE, and sets the CPU as being PAE capable. Using this parameter
  > will taint the kernel with TAINT_CPU_OUT_OF_SPEC.
    (source: https://patchwork.kernel.org/patch/3789931/ )

CONFIG_IA32_EMULATION=y (x84_64 arch)
=====================

  Include code to run legacy 32-bit programs under a 64-bit kernel.

  All 64bit kernels should have this option enabled..
  
# CONFIG_IA32_AOUT is not set (x84_64 arch)
=============================

  Linux used a.out until libc4. With libc5 (around 1996?)
  Linux moved to ELF. So unless you want to run some binaries from the mid-nineties,
  you are safe without a.out support.
  
  http://unix.stackexchange.com/questions/38385/what-does-config-ia32-aout-do-actually

CONFIG_X86_X32=y  (x84_64 arch)
==============

  x32 ABI for 64-bit mode.
  
  Experimental in kernels 3.4-3.8. Stable in kernels 3.9+
  
  This requires binutils 2.22+... basically Ubuntu Precise+, Slackware 14.0+

  It's should be enabled..

CONFIG_OVERLAY_FS=y
===================

  Overlayfs (Overlay Filesystem) differs from other union filesystem implementations in that
  after a file is opened all operations go directly to the underlying, lower or upper, filesystems.
  This simplifies the implementation and allows native performance in these cases.

  The option to enable OverlayFS exists in Linux kernels 3.18 and higher.

